Transformer



vMay 19, 1 942. 7 A, u, WELCH, JR 2,283,712-

' TRANSFORMER Filed Sept. 20, 1940 Inventor; Alarwscvm U.W J

His Atia- "7 which is provided Patented May 19, 1942 TRANSFORMER Alanson- U. Welch, In, Pittsfleld, Mass., assignor to General Electric Company, a corporation of New York Application September 20, 1940, Serial No. 357,601 7 Claims. (Cl. 171-119) My invention relates to transformers, and particularly to adjustable reactance'transformers.

Heretofore, transformers such as have application in arc welding equipment, have been made with a movable winding or an adjustable shunt inorder to vary the reactance of the transformer so as tocontrol the current drawn from the secondary winding. In order, however, to obtain a relatively large variation in current. with such a transformer it is necessary to employ an adjusting arrangement which will provide a relatively long travel for the movable coil or shunt.

It is, therefore, an object of my inventionto provide a transformer with an improved arrangement for varying the reactance thereof.

Another object of my invention is to provide an improved transformer in which a relatively wide range of reactance may be obtained for a given size transformer.

Further objects and advantages of my invention will become apparent from the following description referring to the accompany drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming ,a part of this specification.

In the drawing, the single figure illustrates a side elevation in partial section of a transformer with an embodiment of my invention.

In the illustrated arrangement, I have employed a transformer with the usual primary and secondary windings, one of the windings, such as the primary winding, being movable in order to vary the reactance or the leakage fluxbetween the primary and secondary windings. However, to give an increased reactance range windings and again moving the primary winding and movable auxiliary winding over'their full range of movement a second portion of the reactance range may be covered. The auxiliary windings may bepmportioned in any suitable I manner so as to obtain the desired ratio. For example, areactance range may be obtained with my improved structure which is double that which could be obtained by the mere movement of the primary winding only. Furthermore, it will be seen that since the auxiliary windings are 7 used to decrease the output current, the size of the conductors which make up the auxiliary windings may be much smaller than those employed for the main windings, due to the fact that they carry a reduced current.

Referring to the drawing, the transformer includes a core [0, a primary winding II, and a secondary winding l2, which are enclosed in a suitable casing l3. Either of these main windings, may be mounted in any suitable manner for movement relative to the other winding, such as I provide a pair of auxiliary windings, one being movable and magnetically coupled with the primary winding, and the other being stationary and magnetically coupled with the secondary winding. These auxiliary windings are 0011? nected in series and so disposed that current flows through them in opposite directions so that they will not vary substantially the-transformation ratio of the transformer. Leads are provided for connecting the load across either the secondary winding alone or across the series circuit including the secondary and auxiliary windings. By

connecting the load across the secondary winding only and moving the primary winding its full distance away from the secondary windingcne portion of the range may be obtained. By connecting the load across the series circuit which includes the secondary winding and the auxiliary such as by bolts 22. In order to rotate the screw according to the arrangement described and claimed in Patent 2,009,800, to Hendricks,whlch is assigned to the same assignee as this present invention. Thus, a winding leg 14 of the core III has a central longitudinal space I! in order to accommodate an adjusting mechanism which includes a screw It, and a traveling nut H. The screw I6 is provided with threads on the major portion thereof and when rotated it is prevented from moving longitudinally by thrust bearings H which are supported by the casing l3. The nut i1 is internally threaded to cooperate with the threads on the screw it, and the nut I1 is arranged to support the primary winding ii in any suitable manner. As shown, the winding coil Il may be clamped between boards I9 and 20, of any suitable insulating material by bolts H. The traveling nut I1 is in turn secured to the adjacent board I! in any suitable manner,

IS a suitable handle 23 may be provided on the end of the screw which projects through the casing [3. It will be seen, therefore, that as the handle is rotated the screw will rotate and since it is prevented from moving longitudinally due' to the thrust bearings IS, the nut II will travel along the screw it as the nut is prevented from il'gtating due to the constricted size of the space When the primary winding II is relatively close to the secondary winding I! the leakage flux will be confined to a relatively narrow path, causing a relatively high current flow in the secondary winding. However, as the primary winding is moved away from the secondary winding the leakage flux is allowed a path of larger cross section, thus increasing the reactance of the transformer and, therefore causing a relatively lower current to be drawn from the secondary winding for a given primary voltage. Of course, when the primary winding i moved as far as it can be for a given size transformer unit, the maximum reactance will be obtained with the connection including the secondary winding only. The reactance ratio due to this movement may be for example, 3:1, depending upon the size of the unit and amount of travel of the primary windmg,

In order that the primary winding may be suitably connected to a source of supply, leads 2% and 25 extend through bushings 2E and 2?, respectively, which are provided in a wall of the casing l3. Suflicient slack is provided in the leads 24 and 25 so that they will not impede the movement of the primary winding. The secondary winding leads 28 and 2d are brought through bushings Hand 3! for connection to any suitable load, such as an arc welder.

In the use of an adjustable reactance transformer in an applicat on such as in an arc welding unit, it is desirable to have a much greater range of reactance for a given size transformer than can be obtained by the mere movement of a winding. In order, therefore, to increase the reactance ratio, I provide a pair of auxiliary windings 32 and 33 connected in series with the secondary winding and so disposed around the winding leg M of the core iii that the current flow therethrough is in opposite directions. The .ux liary windings may have substantially the cane electrical characteristics, such as having the same number of turns so that the total voltage at no load across the series circuit lncluding the secondary and auxiliary windings is the same as that across the secondary winding alone. The auxiliary windings and may be connected in series in any suitable manner, such as, through a flexible conductor 3%! having sufflcient slack so that it will not impede the movement of the coil 32. An insulating block which is attached to the casing 53 may be provided for supporting a part of the flexible cable One of the auxiliary coils, such as the coil 32, may be mounted in any suitable manner, such as being closely coupled with the movable primary winding ii and is mounted for movement therewith in any suitable manner. The auxiliary winding 32 may be fitted tightly around the primary coil H and further secured thereto by insulation wrapping 38. Similarly the auxiliary winding 33 may be mounted in any suitable manner, such as being closely coupled with the secondary winding l2 and may be fitted tightly therearound and tied thereto by insulation wrapping 38'. Furthermore, the auxiliary winding 33 is connected to one end of the secondary winding 8?. as by connection 31 to lead 28. Preferably the winding 33 conducts current around the winding leg [4 in the same direction as the current flow through winding l2 while current flow through winding 32 is opposite to that through winding H.

In order that any suitable load may be connected across the series circuit which includes the secondary winding and the auxiliary windings, a flexible lead 39 extending from the end of the auxiliary winding 32 is brought through the suitably-arranged casing bushing 38. Thus the load may be connected across the secondary winding through leads 28 and 29 or across the series circuit which includes the secondary wi ch ing and both the auxiliary windings 32 and through leads 29 and 39.

The operation of my adjustable reactence transformer is as follows: In order to obtain tin. first step of current range, the load is connected across the secondary-winding only with the primary winding close to the secondary winding. Then as the primary winding is moved away from the secondary winding, the reactance begins to rise since the width of the path for the leakage flux between the primary and secondary windings is thereby increased. This operation will, therefore, lower the current being drawn from the secondary winding, and when the primary winding is moved to the end of its range of travel away from the secondary winding, the largest reactance will be obtained for this particular connection. In order, therefore, to obtain a further increase in the reactance ratio the load is connected across the series circuit includ ing the auxiliary windings and the secondary winding through leads 29 and 39 and the primary winding adjusted again through its movement range. It will be seen that this latter connec tion increases the number of turns acting upon the leakage magnetic flux path. For any given position of the movable coil the leakage reactance is increased approximately a the square of the ratio of turns in the secondary winding plus one auxiliary winding to the turns in the secondary winding only. Thus, by suitably proportloning the windings, this latter connection of the load across auxiliary windings and secondary winding and with the primary winding positioned close to the secondary winding, may give approximately the same reactance as that obtained when the load is connected across the secondary winding only and the primary winding positioned most remote from the secondary winding. When the load is connected across the leads 2:! and the handle 23 may be again rotated to move the primary winding upwardly or away from the scc-- ondary winding in order to further increase the reactance of the transformer, u

Thus, if the change of reactance by the move-- merit of the primary winding with the load con nected across the secondary winding only in the ratio of, for example, 3:1, an additional change in reactance of, for example, 3:2, may be effected by connecting the load across the series circuit including the auxiliary windings and the secondary winding and by again moving the primary winding from its lowermost to its uppermost position. The total range of reactance for the device will therefore be 9:1. In this manner a relatively large ratio of minimum to maximum reactance may be obtained for a given size transformer unit.

It will be understood, of course, that the auxiliary coils 32 and may be arranged connection in series with the primary winding instead of in series with the secondary winding as shown and the same result would obtain. Also, the secondary winding could be made movable and the primary winding held stationary. Furthermore, the auxiliary coil adjacent the secondary winding may be provided with more turns than the auxiliary coil adjacent the primary winding in order to obtain a somewhat higher secondary voltage when on the high reactance connection. This is of some advantage in arc welding transformers in that it tends to improve arc stability, since a higher voltage is desirable at lower current for good welding.

It will be seen, therefore, that I have ,provided a variable reactance transformer with an improved structure for obtaining a relatively wide reactance range for a given size unit. This is accomplished by providing a movable winding and a pair of auxiliary coils which are connected in series and disposed so that current flow through the coils will be in opposite directions. These coils are adapted to be connected in series with the secondary winding, and different reactance ranges may be obtained by connecting the load across either the secondary winding or across the circuit including the auxiliary windings and the secondary winding. The primary winding and the auxiliary winding adjacent thereto are made movable in' order to adjust the size of the leakage flux path.

Modifications of the particular arrangements which I have disclosed embodying my invention will occur to those skilled in the art, so that I do not desire my invention to be limited to the Particular arrangements set forth and I intend in the appended claims to cover all modifications which do not depart from the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An adjustable reactance transformer including primary and secondary main windings, a pair of auxiliary windings, said auxiliary windings having substantially the same electrical characteristics and being disposed so that current flow therein is in opposite directions, means for moving one'of said main windings and one of said auxiliary windingsfor varying the leakage flux path between said primary and secondary windings, means for connecting one of said main windings across a load to obtain a range of reactance during movement -of said movable windings, and means for connecting said one of said main windings and said auxiliary windings in series with a load in order to obtain a second range of reactance during movement of said movable windings.

An adjustable reactance transformer including primary and secondary main windings, one of said windings being movable with respect to the other, a pair of auxiliary windings having substantially the same number of turns; said auxiliary windings being disposed so that' current fiow therein is in opposite directions, means for supporting one of said auxiliary windings to move with said movable main winding so as to vary the leakage flux path between said primary and secondary windings, means for connecting the stationary of said main windings across a load to obtain a range of reactance during movement of said movable windings, and means for connecting the stationary of said main windings connecting said secondary winding across a load to obtain a range of reactance during movement of said movable windings, and means for connecting said secondary winding and said auxiliary windings in series with a load so that a second reactance range may be obtained upon movement of said movable windings.

4. An adjustable reactance transformer including primary and secondary windings, a pair o a a y w d gs having substantially the same number of turns, one of said auxiliary windings being adjacent said primary winding and said other auxiliary winding being adjacent- .ing for connection with a load.

5. An adjustable reactance transformer including primary and secondary windings. a pair of auxiliary windings having substantially the same number of turns, one of said auxiliary windings being adjacent said secondary winding and disposed so that current flow therethrough is in the same direction, the other of said auxiliary windings being adjacent said primary winding and disposed so that current flow therethrough is in a direction opposite to that in said auxiliary winding adjacent said secondary winding, means for supporting said primary winding and said adjacent auxiliary winding for movement relative to said secondary winding and said adjacent auxiliary'winding so that the leakage flux path between said primary and secprimary and secondary main windings surroundand said auxiliary windings in series with a load in order to obtain a second range of reactance during movement of said movable windings.

3. An adjustable reactance transformer including primary and secondary windings, a pair of auxiliary windings having substantially the same number of turns, said auxiliary windings being disposed so that current flow therein is in opposite directions, means for supporting said primary winding and one of said auxiliary windings for movement relative to said secondary winding and said other auxiliary winding so tha the leakage flux path between said primary and secondary wi n s m y be varied, means for ing said winding leg, apair of auxiliary windings having substantially the same electrical characteristics, saidauxili'ary windings being disposed so that current flow therein is in opposite directions, means for moving one of said main windings for varying the leakage flux path be tween said primary and secondary windings, means for connecting one of said main windings across a load to obtain a range of reactance during movement of said movable winding, and meansforconnecting said last mentioned one of said main windings and said auxiliary windings in series across a load in order to obtain a second range of reactance during movement of said movable winding.

7. An adjustable reactance transformer including primary and secondary windings, a pair one of said auxiliary windings being closely coupled magnetically with said primary winding and thesecond of said auxiliary windings being close- 1y coupled magnetically with said secondary winding, means for supporting said primary winding and said first-mentioned auxiliary winding for movement relative to said secondary Winding and said secondary auxiliary winding, a pair of leads connected to said secondary winding, a pair of flexible leads connected to the ends of said first-mentioned auxiliary winding, one of said flexible leads being connected to a stationary terminal and the second of said flexible leads being connected to one end oi! said second auxiliary winding, means for connecting Y 

